1. Field of the Invention
The present invention is directed to a roof assembly for a building which is provided with insulation.
2. Description of Related Art
Presently, in the metal building industry, two main energy conservation code and guidelines are followed by most metal building erectors. First is the International Energy Conservation Code (IECC) and second is the Standard 90.1 promulgated by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE). Both of these standards seek to encourage energy efficiency in the metal building industry for environmental benefit, and the benefit of the users of such metal buildings through the resultant energy cost savings.
These standards, and the United States Department of Energy (DOE), set forth the desired U-factor values for metal buildings. These values are set to increase approximately 30% over the next three years. The current approved standard for most non-residential metal buildings in roofs and ceilings is U-0.065 (R-15.38) which is 6″ Faced Fiberglass installed over and perpendicular to the purlins. This increase will improve the current approval standard to U-0.055 (R-18.2) or U-0.049 (R-20.4) for most ASHRAE climate zones. The U-factor is the inverse, or reciprocal, of the total R-Value, i.e.: U-factor=1/Total R-Value. The R-Value is the thermal resistance to heat flow. A larger R-Value means that the material has greater thermal resistance and more insulating ability as compared to a smaller R-Value. Such R-Values can be added together. For instance, for homogeneous assemblies, the total R-Value of an insulation assembly is the sum of the R-Value of each layer of insulation. These layers may include sheathing and finishes, the insulation itself, air films and weatherproofing elements.
Presently, conventional insulation material that is used in the metal building industry is 6 inches thick, faced fiberglass insulation bans, which have an R-19 rating. FIG. 1 shows a conventional insulated roof assembly 1 for a metal building which has been assembled in accordance with IECC Metal Building Assembly requirements. As can be seen, a standing seam 3 with fiberglass insulation 5 is provided. Thermal blocks 7 are R-5 rigid insulation materials which are supported on purlin 9, purlin 9 being the structural members that support the standing seam roof clip 6 and the roof panel 2. Correspondingly, the R-19 fiberglass insulation 5 is draped perpendicularly across the purlins 9. The thermal blocks 7 are then placed above the purlin/insulation, and the standing seam roof clip 6 is secured to the purlins 9, the roof panel 2 being secured to the standing seam roof clip 6. However, when such faced fiberglass insulation is installed in metal buildings as required by the IECC, the actual measured R-Value is substantially less. In this regard according to the North American Insulation Manufacturers Association (NAIMA), for faced fiberglass insulation 5 that are approximately 6 inches thick, U-0.065 and R-15.38 was measured which does not meet the noted standards of U-0.055 or U-0.049.
Therefore, there exists an unfulfilled need for an insulated roof assembly that can meet the increased IECC and ASHRAE Standards for metal buildings without the need for a drastic change in current building practices.